This invention relates to catalyst systems and processes of using the same, and more particularly to catalyst systems for making alkyl substituted compounds.
In the synthesis of organic compounds, protection groups are used extensively. Protection groups are used to mask specific functionality which then allows other transformations to be effected in the molecule. After the intended transformation is carried out, the protected functionality is then regenerated by removal of the protecting group. The hydroxyl functionality has been found to be effectively protected by transformation to the silyl ether by reaction with alkyl chloro silanes.
Alkyl chloro silanes have been prepared by several methods. One method involves reaction of an alkyllithium with a dialkyl dichloro silane as illustrated below: 
The resulting product is the trialkyl chloro silane. Preparation of alkyllithium requires access to lithium industry specific plant equipment and knowledge of handing pyrophric materials on plant scale. See U.S. Pat. No. 5,332,853 to Morrison et al.
Many preparations of alkyl chloro silanes involve chlorination of a trialkyl silane or trialkyl silanol in the last step, as illustrated below: 
Unfortunately, preparation of the starting trialkyl silane or trialkyl silanol usually requires several steps and is hence economically unfavorable. See, for example, JP 62022790, JP 60222492, JP 08291180, JP 08119978, EP 652,221, EP 556,802, EP 557,762, JP 06247987, JP 06128274. See also EP 298,487 and U.S. Pat. No. 5,312,949. See also EP 278,368.
Another preparation of alkyl chloro silanes involves reaction of an alkyl magnesium halide with a dialkyl dichloro silane in the present of a catalyst, as illustrated below: 
The catalyst of choice to effect reaction is Cu(I)CN. See, for example, JP 0831183, JP 08333374. See also EP 656,363, EP 405,560, and U.S. Pat. No. 4,650,891. Due to the highly toxic nature of Cu(I)CN, industrial preparation of alkyl chloro silanes using an alkyl magnesium process requires experience using toxic materials on industrial scale.
The present invention provides catalyst systems useful in the production of substituted compounds, including alkyl substituted silane compounds. The catalyst systems of the invention include at least two components. A first component can be a copper (I) or (II) halide, and preferably is copper (I) or (II) chloride. At least one additional metal salt which is different from the copper halide is also present as a catalyst in the mixed catalyst system of the invention. Exemplary metal salts include Group IA, Group IIA, Group IIIA, Group IVA and transition metal salts. The anion of the metal salt can vary, but in one currently advantageous embodiment of the invention, the anion is a cyanide anion.
The mixed catalyst systems of the invention are useful in the production of substituted silanes. In this regard, the present invention also provides a process in which a silane of the formula RyHzSiX4xe2x88x92yxe2x88x92z is reacted with an alkyl magnesium halide of the formula R1MgX1, wherein each R and R1 is independently selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, cycloalkyl and substituted cycloalkyl, each X is independently selected from the group consisting of halides and alkoxides, X1 is halide, and y and z can each independently be 0, 1, 2 or 3, in the presence of a mixed catalyst system.
The present invention can provide several advantages. For example, the mixed catalyst systems can be cost effective sources of catalytic activity. Further the present invention can minimize exposure to reagents such as cyanides reagents without detrimental impact on catalytic activity. Further the mixed catalyst system can offer increased flexibility in selection of catalyst reagents.
The processes of the invention for making substituted silanes include reacting a silane of the formula RyHzSiX4xe2x88x92yxe2x88x92z with an alkyl magnesium halide of the formula R1MgX1, wherein each R and R1 is independently selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, cycloalkyl and substituted cycloalkyl, each X is independently selected from the group consisting of halides and alkoxides, X1 is halide, and y and z can each independently be 0, 1, 2 or 3, in the presence of a mixed catalyst system. In particular, it has been discovered that a mixed catalyst system comprising a copper (I) or (II) halide and a Group IA, IIA, IIIA, IVA, or transition metal salt of an appropriate anion catalyzes the reaction of alkyl magnesium compounds with substituted silanes, including alkyl halo silanes.
A currently preferred copper halide is copper chloride. The metal salt includes salts of Groups IA, IIA, IIIA, and IVA metals of the Periodic Table of Elements, namely, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, Sn, Pb, as well as salts of transition metals such as Fe, Zn, Ti, and Zr, and the like. Exemplary anions useful in the metal salt of the mixed catalyst system of the invention include without limitation Clxe2x88x92, Fxe2x88x92, R3Oxe2x88x92, R3CCxe2x88x92, NCSxe2x88x92, CNxe2x88x92, X4Oxe2x88x92, Ixe2x88x92, Brxe2x88x92, R3CO2xe2x88x92, C2O2xe2x88x922, CuCl4xe2x88x92, Oxe2x88x922, and R3xe2x88x92, wherein each R3 is independently selected from the group consisting of alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, aryl and substituted aryl and each X is halide.
The reaction can be conducted in a polar or mixed polar/hydrocarbon solvent system, typically at a temperature from about room temperature up to reflux, although reaction temperatures can be outside of this range. Exemplary polar solvents include, but are not limited to, diethyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, and the like, and mixtures thereof. Exemplary hydrocarbon solvents include, but are not limited to, inert liquid alkanes, cycloalkanes and aromatic solvents, and mixtures thereof. Exemplary alkanes and cycloalkanes include those containing five to 10 carbon atoms, such as pentane, hexane, cyclohexane, methylcyclohexane, heptane, methylcycloheptane, octane, decane and the like and mixtures thereof. Exemplary aromatic solvents include those containing six to ten carbon atoms, such as toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, n-propylbenzene, isopropylbenzene, n-butylbenzene, and the like and mixtures thereof. A currently preferred solvent is tetrahydrofuran (THF). Each catalyst is present in an amount ranging from about 0.01 to about 15 mole percent, and preferably from about 0.1 to about 1 mole percent.
As used herein, the term xe2x80x9calkylxe2x80x9d refers to straight chain and branched C1-C25 alkyl. The term xe2x80x9csubstituted alkylxe2x80x9d refers to C1-C25 alkyl substituted with one or more lower C1-C10 alkyl, lower alkoxy, lower alkylthio, or lower dialkylamino. The term xe2x80x9ccycloalkylxe2x80x9d refers to C3-C12 cycloalkyl. The term xe2x80x9csubstituted cycloalkylxe2x80x9d refers to C3-C12 cycloalkyl substituted with one or more lower C1-C10 alkyl, lower alkoxy, lower alkylthio, or lower dialkylamino. The term xe2x80x9carylxe2x80x9d refers to C5-C25 aryl having one or more aromatic rings, each of 5 or 6 carbon atoms. Multiple aryl rings may be fused, as in naphthyl or unfused, as in biphenyl. The term xe2x80x9csubstituted arylxe2x80x9d refers to C5-C25 aryl substituted with one or more lower C1-C10 alkyl, lower alkoxy, lower alkylthio, or lower dialkylamino. Exemplary aryl and substituted aryl groups include, for example, phenyl, benzyl, and the like.
The current invention has been shown to be particularly useful in the preparation of t-butyl dimethyl silyl chloride, a chloro silane which is commonly used on industrial scale in the pharmaceutical industry. Reaction of t-butyl magnesium chloride with dichlorodimethylsilane resulted in t-butyl dimethyl silyl chloride (TBSCl) preparation in 90% yield using the current invention. This result was obtained employing the mixed catalyst of Cu(I)Cl and KCN as the metal salt. No product formation is observed in the absent of a catalyst. Typical results obtained employing Cu(I)Cl (alone) are 20-30% yield. 
In addition to above mixed catalysis, other solvent additives can be added to help solubilize the slightly insoluble copper cation. Such additives or modifiers are known in the art and include without limitation trialkyl amines, tetramethylethylenediamine (TMEDA), diethylenetriamine, triethylene tetraamine and N-alkyl capped derivatives thereof, and the like as well as mixtures thereof.
Other modifiers can also be added to solubilize and more importantly disassociate the row IA, IIA, IIIA, IVA or transition metal from its anion. These modifiers include without limitation crown ethers such as 18-crown-6, 12-crown-4, and their substituted derivatives, cryptand complexing agents, and various glymes such as monoglyme, ethyl glyme, diglyme, ethyl diglyme, triglyme, butyl diglyme, tretraglyme, and polyglyme, and the like and mixtures thereof.
The current invention is a very cost effective source of catalytic activity. If addition of a single copper salt or single entity, in which the appropriate catalytic anion desired is already present as the counter ion on copper, were added as a single compound, the single entity catalysis would be more expensive to prepare. For instance, if the use of copper (I) cation in the present of phenyl acetylide anion were desired, one would have to prepare copper (I) phenyl acetylide from an appropriate copper derivative and lithium or sodium phenyl acetylide which would be cost ineffective. In addition to the cost of preparing a single entity catalysis, double handling of a toxic anions such as CNxe2x88x92 would certainly be disadvantaged. 
The current invention also allows infinite flexibility of the catalyst system which is not available from the single entity approach. It has been speculated by some authors that in copper systems, the anion adds to the silyl derivative to form a pentacoordinated silicon atom which is then more susceptible to nucleophilic attach by alkyl magnesium compounds. Patrick Lennon, David Mack, Quentin Thompson, Organometallics, 1989, 8, 1122; Robert Corriu, Christian Guerin, Bernard Henner, W. W. C. Wong Man, Organometallics, 1988, 7, 237. Copper cations can also exchange with alkyl magnesium compounds to form alkyl copper derivatives. H. O. House, W. L. Respess, G. M. Whitesides, J. Org. Chem., 1966, 31, 3128. Both of the above potential catalytic activities could effect reaction in combination. Therefore, when making use of a single entity approach, one does not have the flexibility of varying the ratios of copper to the catalytic anion, which would be important if the catalysis regeneration rate were different for each of the two species. While employing the mixed catalysis system, use of the two catalytic agents can be varied to account for a difference in catalyst regeneration rate. The current invention""s reagent flexibility would also be of advantage to reduce the quantity of toxic catalytic species, such as CNxe2x88x92 used as the catalytic anion, when carrying out these transformations on industrial scale given the appropriate catalysis regeneration rates for the given species.
The present invention is described above as useful in the production of substituted silanes. However, the mixed catalyst systems of the invention may be useful in substitution, or alkylation, reactions of metal or metalloid substrates generally (in addition to alkoxy silanes or halosilanes), including alkyl-halogen exchange reactions involving halogen or alkoxy containing Group IVA or Group VA compounds. For example, the mixed catalyst system of the invention may also be useful in the production of organosilicone compounds, organotin compounds, alkyl or aryl phosphines, and the like. Thus the catalyst systems of the invention can be used to alkylate compounds of the formula RyHzAX4xe2x88x92yxe2x88x92z or RyHzBX3xe2x88x92yxe2x88x92z, in which R, H, X, y and z are the same as defined above, A is an element from Group IVA of the Periodic Table of Elements, including silicon, carbon, germanium, and tin, and B is an element from Group VA of the Periodic Table of Elements, including phosphorous.
The mixed catalyst systems of the invention can also be useful in substitution reactions involving a halogen or alkoxy containing transition metal reagent, such as those used in the production of ligands, metallocene catalysts (in which a hydrocarbon such as a cyclopentadienide is reacted with a transition metal halide) and the like.
The mixed catalyst systems are particularly useful for alkylation processes in which a bulky or highly hindered substituent, such as a tertiary hydrocarbyl group, is added to a halogen containing Group IVA or Group VA compound or transition metal halide. Tertiary hydrocarbyl groups include without limitation tertiary alkyl groups such as tert-butyl, 1,1-dimethylpropyl, and 1,1-diethylpropyl, and aryl-group containing tert-alkyl groups, such as 1,1-dimethylbenzyl. Other bulky groups include isopropyl, 2-ethylhexyl, n-octyl, and the like.
Exemplary organosilanes include without limitation t-butyldimethylchlorosilane, t-butylsilane, t-butyltrichlorosilane, di-(t-butyl)dichlorosilane, di-(t-butyl)methylchlorosilane, di-(t-butylsilane), t-butyldiphenylsilane, t-butyldiphenylchlorosilane, triisopropylsilane, triisopropylchlorosilane, and the like and mixtures thereof.
Exemplary organogermanes include without limitation t-butyldimethylchlorogermane, t-butylgermane, t-butyltrichlorogermane, di-(t-butyl)dichlorogermane, di-(t-butyl)methylchlorogermane, di-(t-butylgermane), t-butyldiphenylgermane, t-butyldiphenylchlorogermane, triisopropylgermane, triisopropylchlorogermane, and the like and mixtures thereof.
Exemplary organotins include without limitation t-butyldimethylchlorotin, t-butyldimethyltin, t-butyldiphenyltin, t-butyldiphenylchlorotin, di-(t-butyl)-dichlorotin, triphenylchlorotin, tri-n-octyltin, and the like and mixtures thereof.
Exemplary phosphines include without limitation tri-(isopropyl)phosphine, tri-(t-butyl)phosphine, tri-(1-naphthyl)phosphine, di-(t-butyl)chlorophosphine, di-(t-butyl)phosphine, di-(isobutyl)phosphine, and the like and mixtures thereof.
The following examples serve to illustrate the invention but are not intended to be limitations thereon.